The present invention relates to longitudinal quartz crystal resonators having an intermediate oscillating frequency range from 500 KHz to 4.2 MHz, and more specifically relates to the shape of the resonator, structure of the driving electrodes and cut angle. Recently, intensive research has been undertaken for this type of resonator. The longitudinal quartz resonator is most suitable for a clock signal source in portable devices such as as paging device and IC card.
The conventional longitudinal quartz crystal resonator is comprised of a vibrational portion and a supporting portion formed integrally with each other by an etching method. The supporting portion has a uniform width, extends in a unidirection and is mounted at its rear section. Therefore, energy of the vibrational portion is transmitted to the mounting section, thereby causing vibration energy loss. Consequently, it is difficult to produce a longitudinal quartz crystal resonator having a small equivalent series resistance R.sub.1.
Another type of conventional non-longitudinal quartz crystal resonator is disclosed in U.S. Pat. Nos. 4,484,382 and 4,633,124. This type of resonator has a specific supporting portion designed to suppress vibration energy loss.
As mentioned above, the conventional shape of longitudinal quartz crystal resonator causes a considerable vibration energy loss. Consequently, it is difficult to form the longitudinal quartz crystal resonator having a small equivalent series resistance R.sub.1. In addition, a reduction of the size for an increase in oscillating frequency would seriously affect various electric characteristics of the supporting portion to thereby hinder the oscillating feature of the resonator.